Reducing the amount of energy consumption by a fluid-handling machine for cleansing articles in a liquid, such as a clothes washer, is a significant problem, in part because of increasing worldwide energy demand. In such a machine, the amount of energy consumed is primarily determined by the amount of energy needed to heat the liquid, such as water, used to cleanse the articles. Thus, decreased liquid consumption for such machines can result in a significant improvement in energy efficiency.
Appliances, such clothes washers, typically receive liquid for a predetermined duration through a conduit connected to the machine. A wash cycle for such a machine may comprise providing substantially particle-free liquid to the machine, circulating or distributing the liquid during the wash cycle, and draining or flushing the liquid from the machine after being used to wash the articles. Typically, a machine user has limited control over the amount of liquid provided for a wash cycle, such as by selection from a few predetermined options. Such a machine does not use liquid efficiently because variations in liquid pressure or degradation in machine components generally require providing liquid for an excessive duration to ensure more than a sufficient amount for a wash cycle. Closed loop feedback control is one method to improve water conservation in clothes washers. Several devices are available to monitor or measure the amount or volume of liquid provided for a wash cycle.
Devices for measuring the amount of liquid, such as water, include flowmeters that measure the water flow rate to the clothes washer and water level sensors that detect the static air pressure in an air cavity in the sensor. However, such devices may be difficult or non-economic to implement, may be unreliable, may degrade over time, and may not provide robust measurements relative to the machines incorporating them. Furthermore, the accuracy of such devices is not entirely satisfactory due to variations in the amount of liquid needed to satisfactorily cleanse varying amounts of soiled articles.
A need thus exists for a machine for cleansing articles incorporating a closed loop feedback system for monitoring and controlling the amount of liquid provided for a wash cycle.